1. Field of the Invention
The present invention relates to an improved method and apparatus for injection molding of thermoplastic materials. More particularly, the present invention relates to an improved apparatus for injection molding having an improved clamping unit. Most particularly, the present invention relates to an improved apparatus for injection molding which comprises a stand alone injection molding unit in combination with a separate, detachable, horizontal booking press to provide a readily movable clamping unit having easy access to both halves of the injection mold.
2. Discussion of the Related Art
Injection molding has long been a preferred method of molding where high production rates, fully automatic operation, and reduced material costs are considerations. Further, a wide range and combination of colors can be molded. Materials customarily molded by the injection method includes cellulose acetates, cellulose acetate-butyrate, polystyrene, polyvinyl chloride, acrylic and vinylide chlorides.
The presently known injection molding machine consists of two basic components. The injection or plasticizing unit, and the clamping unit. The injection unit is where the raw material, usually in pellet form, is converted, melted, or plasticized to a condition where it can be injected into the mold. A reciprocating screw is used to convey the material to the front of the screw. Once the material has collected in front of the screw, hydraulic pressure forces the screw forward, thereby injecting the plastic into the mold.
The clamping unit is the mechanism on which the molding dies are mounted, and applies the force to the mold during the injection cycle to prevent the molds from being forced apart. Injection molding pressures can exceed 30,000 pounds per square inch, so the clamp must be able to maintain high pressure in order to keep the mold closed during injection.
Injection molding machines are widely known in the art. Commonly used injection molding machines are those available from Hettinga Equipment, Inc., Des Moines, Iowa 50332, Cincinnati Milicron, Batavia, Ohio 45103, Husky Injection Molding Systems, Inc., Bolton Ontario, Canada L7E, 5S5 and Toshiba Machine Company of America, Elk Grove Village, Ill. 60007.
However, in spite of their popularity, injection molding machines have certain disadvantages because of their large size and the high pressures used in injection molding. This has led to rather large high cost units with fairly inaccessible molding dies. Even though injection molding may be favored for certain applications, the fact that the dies are not easily accessible or interchangeable limits such application.
Also, because injection molding machines are rather large, and not easily moveable, they are usually located some distance away from the end user of such parts, and are not easily located near the end user or on a production line for example. In addition, since the known injection molding dies include a moveable part and a stationary part which are in a closely spaced opposed relationship, such injection molding machines can not easily be used for other than the making of an entire thermoplastic part. For example, they can not easily be used for molding, for example, a polyvinyl chloride part onto a sheet of material because the sheet of material can not easily be inserted in the mold cavity.
Thus, those skilled in the art have continued to search for a way to provide an injection molding unit which lighter, is of a smaller size, has full access to the molding dies, can xe2x80x9cmold ontoxe2x80x9d another part, can be used at or near the point of need, and has easily changeable, or interchangeable clamping units to provide for quick changeover between parts with minimal downtime of the injection or plasticizing unit.
The aforementioned problems are addressed in accordance with the present invention by combining a known plasticizing or injection unit with a horizontal booking press to provide a novel apparatus and method not hereto found in the prior art.
In one embodiment of the invention, a horizontal booking press is connected to an injection or plasticizing unit.
In another embodiment of the present invention, a horizontal booking press is connected to a stand alone injection or plasticizing unit.
In a further embodiment of the present invention, a horizontal booking press is interchangeably connected to a stand alone injection molding unit.
In a further embodiment of the invention, the foregoing horizontal booking press has a first, or moveable, mold platen which may hold, or have affixed to, or carry, a base portion of a mold or molds. A second, or door, platen may hold, have affixed to, or carry, a core or cavity portion of a mold or molds. The second, or door, platen is hingedly connected to the frame of the horizontal booking press to swing open and closed like a cover of a book with respect to the moveable mold platen.
In a still further embodiment of the invention the moveable mold platen is reciprocated or moved by a link and toggle arrangement.
In a still further embodiment of the invention the moveable mold platen is reciprocated or moved by a rack and pinion arrangement.
In a still further embodiment of the invention the moveable mold platen is reciprocated or moved by a ball screw arrangement.
In a still further embodiment of the invention the moveable mold platen is reciprocated or moved by hydraulic cylinders.
In a further embodiment of the invention, an injection molding apparatus of the foregoing nature is provided in which the horizontal booking press is light in weight and easily moveable from place to place as needed.
In a further embodiment of the present invention, an injection molding apparatus of the foregoing nature is provided wherein the whole horizontal booking press is interchangeable with other horizontal booking presses as needed.
In another embodiment of the invention a self-contained injection molding apparatus of the foregoing nature is provided.
Thus, one of the objects of the present invention is to provide a novel molding method and apparatus for injection molding a part.
Another object of the present invention is to provide an injection molding apparatus which has fully accessible mold portions.
Another object of the present invention is to provide a self-contained injection molding apparatus which may produce a part at the site where it is needed, or sufficiently nearby, to essentially save the cost of shipping manufactured parts to the site.
Another object of the present invention is to provide an injection molding apparatus which can injection mold plastic parts onto other parts which may be inserted into the fully accessible mold or mold portion or portions.
Further objects and advantages of the present invention will be apparent from the following description and appended claims, reference being made to the accompanying drawings forming a part of the specification, wherein like reference characters designate corresponding parts in the several views.